A torque detection device is disclosed in Patent Document 1 and the like. The torque detection device of Patent Document 1 includes two magnetic flux collecting rings, arranged in a spaced side by side relation in an axis line direction outside an outer periphery of a magnetic circuit forming member provided in a rotating body which includes an input shaft and an output shaft coupled by a torsion bar, for collecting the magnetic flux generated by the magnetic circuit forming member; and a detector for detecting the torque applied to the rotating body based on the density of the magnetic flux collected by each magnetic flux collecting ring.
The torque detection device configured as above is incorporated in an electric power steering apparatus for a vehicle and the like. The electric power steering apparatus includes the rotating body of which input shaft is connected to a steering wheel; a tubular housing for accommodating and supporting the rotating body; a steering assist electric motor connected to the output shaft by way of a reduction gear mechanism; and a control unit connected to a drive circuit of the electric motor and the detector and configured using a microprocessor, where the detector detects the torque applied to the input shaft when the steering wheel is steered through a torsion generated in the torsion bar, and the drive of the electric motor is controlled based on the detected torque.
When incorporating the torque detection device to the housing, the entire torque detection device is inserted to the inside from one end of the housing, and fixed inside.    [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-149062